In a flexible copper clad laminate use copper foil, when bonding the copper foil to a resin substrate, it is necessary to improve its bonding strength and satisfy required electrical property, etching property, heat resistance, and chemical resistance as a copper clad laminate. For this reason, roughening treatment is applied to the bonding surface of the copper foil to be bonded with the resin layer after the foil is produced (hereinafter sometimes described as the “untreated copper foil”), further zinc (Zn) plating, nickel (Ni) plating, or the like is applied to the top of the roughened surface, still further chromate treatment etc. are applied to the top of the surface plated with the Zn, plated with the Ni, and a variety of other techniques are applied.
Recently, IC mounted boards driving liquid crystal displays of display parts of PCs, mobile phones, and PDAs are becoming increasingly advanced in density. Stability with respect to treatment at a high temperature in the production processes of the same and accurate circuit configurations are demanded. On such demands, in flexible copper clad laminates for producing printed circuit boards, copper clad laminates manufactured by bonding electrodeposited copper foil capable of forming accurate conductive circuits, and polyimide resin layers capable of being used at a high temperature, by thermal adhesion at high temperature of several hundreds of degrees, etc. have been employed.
In this high temperature manufacturing treatment, improvement of the bonding strength of the copper foil with the polyimide resin layer has become the most pressing issue. As a means for solving this problem, the technique of roughening treatment of the surface of the copper foil by a Zn-containing alloy is disclosed in for example Patent Literature 1.
Further, as the flexible copper clad laminate using copper foil bonded with a polyimide resin layer at a high temperature, a surface-treated copper foil obtained by treating the surface of untreated copper foil for bonding with a polyimide resin layer by an electroplating solution containing at least one element selected from among molybdenum, iron, cobalt, nickel, and tungsten and further providing an Ni plating layer or Zn plating layer or else an Ni plating layer plus a Zn plating layer on this plating layer has been proposed (see Patent Literature 2).